Device to improve accuracy of a small arm

ABSTRACT

An insert assembly for a weapon is disclosed. The weapon may be a rifle, such as an M4 carbine. The insert assembly is configured to support a bolt while the bolt moves during recharging and firing cycles. The insert may be configured to continuously press on an upper receiver when the rifle is assembled. These features improve shooting accuracy of the rifle by minimizing and/or making consistent movements of the rifle&#39;s internal components (i.e., there is less wobbling of the components with respect to each other). The insert assembly may include a support plate and a hollow protrusion rigidly attached to the plate. A piston and a spring are inserted into the protrusion. The piston slides within the protrusion and is pushed against the bolt of the rifle by the spring.

FIELD OF THE INVENTION

This application relates generally to firearms and more specifically to an insert for a small arm, typically a rifle, which provides greater accuracy for the weapon.

BACKGROUND

Many firearms, such as the assault rifles commonly used in military and law enforcement situations, are designed by their manufacturers to have a bolt assembly driven in a reciprocal motion between two positions. One example includes the AR-15 family of firearms, which in turn includes the M16-type firearms. The M16-type firearms are military versions and are capable of operating in a fully automatic mode. As originally designed, the AR-15, M16, and M4 firearms are collectively and generically referred to as “M16-type” firearms or rifles. An M16-type rifle includes auto loading features and is capable of operating in a semi-automatic regime, a full-automatic regime, a burst-fire regime, a selective-fire regime, or various combinations of the above. As such, the M16-type rifle is used for a higher volume of firing than many other types of firearms and accordingly may be susceptible to higher levels of heat, fouling, and component failures.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Provided is an insert assembly for installing into small arm, typically a rifle such as an M4 carbine. The insert assembly is received in a lower receiver of the rifle. The insert assembly is configured to support a bolt while the bolt moves during firing and reloading cycles. In some exemplary embodiments, the insert is configured to continuously press on an upper receiver when the rifle is assembled. These features tend to improve shooting accuracy of the rifle by minimizing and/or making consistent some undesirable movements of the rifle's internal components (i.e., there is less wobbling of the components with respect to each other). In some exemplary embodiments, the insert assembly includes a support plate and a hollow protrusion rigidly attached to the plate. A piston and a spring are inserted into the protrusion. The piston slides within the protrusion and is pushed against the bolt of the rifle by the spring.

In some exemplary embodiments, an insert assembly for a rifle includes a support plate configured for insertion into a lower receiver of the rifle, a hollow protrusion rigidly attached to the support plate, a piston inserted into the hollow protrusion, and a spring inserted into the hollow protrusion between the piston and the support plate. A combination of the support plate and the hollow protrusion is sometimes referred to as a body. The piston is sometimes referred to as a “nub pilot” or as a “nubbin.” The support plate has a front surface that contacts the protrusion and a spring. The protrusion, in fact, extends away from the front face of the support plate. The piston is configured to slide inside the hollow protrusion in a direction substantially perpendicular to the front surface. The piston includes a top surface for supporting a bolt of the rifle while the bolt slides over the top surface in a direction substantially parallel to the top surface. The spring is configured to exert a predetermined force on the piston, thereby pushing the piston against the bolt and away from the front surface. In some exemplary embodiments, the top surface of the piston is substantially parallel to the front face of the support plate.

The top surface of the piston may include a chamfer. The chamfer may be used to allow uneven portions of the bolt to slide over the top surface. The chamfer may be also used to locate the bolt keyway when the bolt moves reciprocally between its two working positions during firing and reloading. In certain embodiments, the hollow structure and piston include one or more aligning features for controlling orientation of the chamfer with respect to the support plate and/or the protrusion.

The top surface of the piston may be made of wear resistant stainless steel, such as 17-4 Stainless 43/45 RC. The support plate and protrusion may be made from a more general grade of stainless steel, such as 303 Stainless Steel. The spring is also generally made from stainless steel. The spring may be configured to exert a force of between about 5 lbs. and 15 lbs. on the piston when the top surface of the piston is in the upmost position. In an exemplary embodiment, the spring is configured to exert a force of about 10 lbs. In some exemplary embodiments, the hollow protrusion includes a positive stop feature configured to limit an upmost position of the top surface of the piston. For example, a piston may not need to contact the bolt of the rifle at all times during firing and reloading cycles, and at certain points, a positive stop controls the extension of the piston out of the hollow protrusion. The piston may be configured to extend out of the hollow protrusion less than about 0.5 inches when the top surface of the piston is in the upmost position.

The insert assembly may also include a second protrusion attached to the support plate and extending away from the front face of the support plate in the same direction as the hollow protrusion. The second protrusion includes a second top surface configured to press on an upper receiver of the rifle and exert a force on that receiver when the upper receiver is engaged with the lower receiver (i.e., when the rifle is in an assembled state). A friction created supports the insert assembly with respect to other components of the rifle. This friction may exist between the second top surface and the upper receiver as well as between the support plate and the lower receiver. The second top surface may include a rubber-like compressible material. More specifically, the second top surface may include Santoprene™ TPV 111-35. The second top surface may extend at least about 0.25 inches from the second protrusion prior to engaging with the upper receiver of the rifle. The second top surface is configured to compress by at least about 0.125 inches while engaging with the upper receiver of the rifle.

In some exemplary embodiments, an insert assembly for installing into a rifle includes a support plate configured for insertion into a lower receiver of the rifle and a protrusion attached to the support plate and extending away from a front face of the support plate. The protrusion includes a second top surface configured to press on an upper receiver of the rifle and exert a force on the upper receiver when the upper receiver is engaged with the lower receiver. The friction created by this force supports the insert assembly with respect to other components of the rifle.

The insert assembly may include a support plate, a hollow protrusion, a piston inserted into the hollow protrusion, a spring inserted into the hollow protrusion between the piston and the support plate, and a second protrusion attached to the support plate and having a second top surface. The support plate is configured for insertion into a lower receiver of the rifle. The hollow protrusion rigidly attaches to the support plate and extends away from a front face of the support plate. The piston is configured to slide inside the hollow protrusion in a direction substantially perpendicular to the front surface of the support plate. The piston includes a top surface for supporting a bolt of the rifle while the bolt slides over the top surface in a direction substantially parallel to the top surface. The top surface includes a chamfer configured to locate the bolt keyway when the bolt moves reciprocally between its two working positions during firing and reloading. The spring is configured to exert a predetermined force of between about 5 lbs. and 15 lbs. on the piston, thereby pushing the piston against the bolt and away from the front surface of the support plate. The second top surface of the second protrusion is configured to press on an upper receiver of the rifle and exert a force on the upper receiver when the upper receiver is engaged with the lower receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.

FIG. 1 is a schematic side view of a rifle.

FIG. 2 is a partial schematic cross-sectional side view of a rifle assembly.

FIG. 3 is a general schematic view of a bolt within a rifle.

FIGS. 4A and 4B are general schematic views of a bolt supported by an insert assembly at two different positions of the bolt.

FIGS. 5A and 5B are schematic views of an insert assembly at two different positions of its piston.

FIG. 6 is a schematic perspective view of an insert assembly.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail to not unnecessarily obscure the present invention. While the invention will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the invention to the embodiments.

Various embodiments of the device are configured to improve the accuracy of small arms by removing unwanted motion from the components. While the following description refers generally to a rifle, it will be recognized that the device can also be used in small arms not generally described as a rifle.

Some components of a bolt action rifle will now be briefly described in order to provide a better understanding of various claimed features. FIG. 1 is a schematic side view of a rifle 100 that includes an upper receiver 105 pivotally coupled to a lower receiver 110. Upper receiver 105 includes a barrel 115 that may be attached to upper receiver 105 using threaded or other types of mechanical couplings. Barrel 115 has a front sight assembly 120 securely attached thereto and is partially enclosed by a pivotable hand-guard assembly 125. Hand-guard assembly 125 is pivotally mounted to barrel 115 using a pivot pin 165. Barrel 115 has a gas port passing inside and through the top portion of barrel 115 to communicate with a gas cylinder assembly 130. Certain details of the gas port and gas cylinder assembly are further described below in the context of FIG. 2.

Upper receiver 105 and lower receiver 110 are braced by the butt-stock assembly 135, which is attached to lower receiver 110 using threaded or other types of mechanical couplings. A handgrip 140 is attached to lower receiver 110 directly behind a trigger assembly. A removable magazine 145 is fitted into a magazine well of lower receiver 110. A rear sight assembly 150 is adjustably mounted on upper receiver 105. A charging handle 155 is attached to upper receiver 105 and is used to engage bolt assembly 160. As can be seen from FIG. 1, a coupling between upper receiver 105 and lower receiver 110 establishes references between various other components of rifle 100. Specifically, a reference is provided between front sight assembly 120, rear sight assembly 150 and barrel 115 secured on upper receiver 105 with respect to butt-stock assembly 135 and handgrip 140 secured on lower receiver 110. This reference may be important while supporting rifle 100 by butt-stock assembly 135 and handgrip 140 and aiming at a target using front sight assembly 120 and rear sight assembly 150, particularly when firing in a continuous mode. Any slop between upper receiver 105 and lower receiver 110 may interfere with this aim and, therefore, needs to be minimized.

FIG. 2 is a partial schematic cross-sectional view of a rifle assembly 200, in accordance with certain embodiments. Assembly 200 is shown with cut-away portions of upper receiver 105 and lower receiver 110.

A bolt carrier 205 carries a bolt 210 and is slidably mounted to upper receiver 105. Bolt carrier 205 is also affixed at the top to a gas key 215, which is used to seal off the gas passages to bolt carrier 205. A gas system 220 includes a cylindrical gas cylinder 225 rigidly mounted to the front sight assembly and containing therein a slidable piston 230 having a dished gas pressure face and being fixedly secured to a slidable piston rod 235. Piston rod 235 extends concentrically down gas cylinder 225 and slidably engages a cylinder nut 240, which is threadably engaged in the left-most end of gas cylinder 225. Gas cylinder 225 and piston 230 may be made of a hard structural material, such as steel or stainless steel. Gas cylinder 225 is closed at the opposite end by cylinder nut 240. The length of gas cylinder 225 varies depending upon the amount of stroke needed to completely cycle the bolt 210 and bolt carrier 205 sufficiently backward in the receiver to eject a fired cartridge and to load a new unfired cartridge into chamber 245. Gas cylinder 225, slidable piston 230, and piston rod 235 are arranged to lay substantially parallel to barrel bore 250 such that piston rod 235 passes through an opening 255 formed in upper receiver 105. Piston rod 235 extends through opening 255 and engages in passage 260.

A bolt contacts a breech and then rotates and locks into a place in which it is being held by lugs attached to the breech or to the barrel extension. Upon closing, the bolt passes through the slots cut in the front of the barrel extension and then rotates. At this point it is locked in place. The bolt remains locked until the action is cycled. This could be performed either manually by the operator or mechanically by the gas system described above in the context of FIG. 2. In this later example, the gas created by discharging the rifle pushes on the bolt carrier. The bolt carrier then rotates the bolt and unlocks it from the breech so that it can be withdrawn in order to extract and eject the spent casing and chamber a new round. It should be noted that rotating bolts are not exclusive to gas-operated weapons and can be found in some bolt-action, lever-action and pump-action rifle designs. As such, various inventive aspects described in this document may be applied to all bolt-type rifles.

A magazine of a typical rifle includes a spring that forces bullets towards the bolt. Compression springs are typically used for this purpose. These springs provide variable forces depending on their compression levels, which in turn depend on a number of bullets remaining in the magazine. Therefore, when the magazine is fully loaded, the force may be much greater then when the magazine is almost empty. The bolt typically has some clearance, which is often referred to as “slop.” The clearance may be needed for the bolt to freely move and to avoid jamming the rifle during firing and recharging. However, a combination of this clearance and a variable force applied to the bolt may cause the bolt to operate differently at different magazine loadings. This in turn may interfere with the shooting precision as further described below.

FIG. 3 is a schematic view of a rifle assembly 300 including a bolt 305, in accordance with an exemplary embodiment. Bolt 305 is configured to move in a direction 310 between two operating positions during firing and reloading. Direction 310 is typically substantially parallel or, more specifically, substantially coaxial to a barrel of the rifle. The clearance in the bolt assembly described above allows bolt 305 to move within that assembly in other directions (e.g., a left-right direction 315 and an up-down direction 320 as shown in FIG. 3). Motion of a bolt in these other directions 315 and 320 is not desirable because it may cause the entire rifle to shake and interfere with shooting accuracy, particularly when shooting in an automatic mode. A force from the magazine's spring helps to push bolt 305 to an upward position. However, this force is variable and causes variations in how much bolt 305 moves in directions 315 and 320. A user may experience gradually increasing vibrations as he continues to shoot and empty the magazine. These vibrations abruptly disappear when the magazine is replaced and shooting is resumed.

It has been found that shooting accuracy may be improved by minimizing unnecessary movements of a rifle's internal components or at least making these movements more constant and less dependent, for example, on the magazine's loading. A specific insert assembly has been designed to exert a constant force on a bolt while it moves between the two operating positions. The insert may be installed into a lower receiver of the rifle. In certain embodiments, the insert is equipped with a rubber button that pushes on the upper receiver of the rifle, thereby producing a constant force between the two receivers and preventing the receivers from moving with respect to each other.

FIGS. 4A and 4B are schematic views of a bolt 405 supported by an insert assembly 420 at two different positions of the bolt 405, in accordance with an exemplary embodiment. In FIG. 4A, bolt 405 is shown in a forward position. In FIG. 4B, bolt 405 is shown in a rearward position.

Bolt 405 will generally have a variable cross-sectional profile. For example, bolt 405 may have a narrow portion 410 and a wider portion 415. While bolt 405 is movable within the rifle, insert assembly 420 is stationary. Insert assembly 420 is configured to exert a force on bolt 405 as bolt 405 moves within the rifle. The force applied is variable according to the strength of the spring selected. The applied force may be about 5 lbs., about 10 lbs, or about 15 lbs. Unlike the force from the magazine's spring which varies with the number of rounds in the magazine, the force exerted by the insert assembly is constant. The amount of applied force may be chosen by the user of the weapon.

FIGS. 5A and 5B are schematic views of an insert assembly 500 at two different positions of a piston 520. Insert assembly 500 includes a support plate 505 configured to be received in a lower receiver of the rifle. Support plate 505 includes a top surface 510 which may be used for reference purposes.

Insert assembly 500 includes a hollow protrusion 515, which may be rigidly attached to support plate 505. As shown in FIG. 5A, hollow protrusion 515 may extend away from the top surface 510 of the support plate. Hollow protrusion 515 may be configured to receive a piston 520, which may slide within hollow protrusion 515 in a direction substantially perpendicular to the top surface 510 of support plate 505. Piston 520 has a top end extending out of hollow protrusion 515 and configured to support a bolt. The piston 520 supports the bolt as the bolt slides over the top surface of the piston 520 in a direction substantially parallel to the top surface 510 of the support plate 505.

The top surface of the piston 520 may have a chamfer 535. Chamfer 535 may be configured to allow uneven portions of the bolt to slide over the top surface. Hollow protrusion 515 and piston 520 may include an aligning feature for controlling the orientation of chamfer 535 with respect to support plate 505. The top surface of piston 520 is substantially parallel to front face 510 of support plate 505.

Insert assembly 500 also includes a spring 525 inserted into hollow protrusion 515 between piston 520 and top surface 510 of support plate 505. Spring 525 may be configured to exert a predetermined force on piston 520 and push piston 520 upward relative to the top surface 510 of support plate 505. Hollow protrusion 515 may include a positive stop feature configured to limit an upmost position of piston 520 such as a base element that contacts a lip of hollow protrusion 515.

Spring 525 may be selected to exert a force as desired by the user. The force may be between about 5 lbs. and 15 lbs. exerted on piston 520 when piston 520 is in the upmost position.

Insert assembly 500 may include a second protrusion 530 attached to support plate 505 and extending away from top surface 510 in the same direction as hollow protrusion 515. Second protrusion 530 includes a second top surface configured to support an upper receiver of the rifle and exert an upward force on the upper receiver when the upper receiver is engaged with the lower receiver. The second top surface may be made from a rubber-like compressible material, such as Santoprene™ TPV 111-35. The second top surface may extend by between about 0.25 inches from top surface 510 of support plate 505 prior to engaging with the upper receiver of the rifle. The second top surface may be configured to compress by at least about 0.125 inches while engaging with the upper receiver of the rifle. If desired for a particular application, insert assembly 500 may include only the second protrusion 530 and no hollow protrusion 515, piston 520, or spring 525.

FIG. 6 is a schematic perspective view of an insert assembly 500 in accordance with an exemplary embodiment. Specifically, the support plate 505 is shown as having the top surface 510 with the hollow protrusion 515 positioned on the top surface 510. The hollow protrusion 515 is shown as receiving the piston 520, which may expand and contract within the hollow protrusion 515 in a direction substantially perpendicular to the top surface 510 of the support plate 505. The piston 520 has a top surface which extends beyond the hollow protrusion 515. Furthermore, the top surface of the piston 520 is shown as including the chamfer 535.

As mentioned above, the hollow protrusion 515 and the piston 535 may include aligning features for controlling orientation of the chamfer 535 with respect to the support plate 505. FIG. 6 shows a slideable arrangement of a channel on the hollow protrusion 515 and a guide on the piston 520 used for alignment. The chamfer 535 may be used to allow portions of the bolt to slide over the top surface as illustrated in FIGS. 4A and 4B. The chamfer 535 may be also used to locate the bolt keyway when the bolt moves reciprocally between its working positions during firing and reloading.

The insert assembly 500 may also include the spring 525 inserted into the hollow protrusion 515 between the piston 520 and the top surface 510 of the support plate 505. The spring 525 may be configured to exert a predetermined force on the piston 520 and push the piston 520 upward relative to the top surface 510 of the support plate 505, thereby providing a stabilizing force for the bolt of the weapon.

The above description is illustrative and not restrictive. Many variations of the invention will become apparent to those of skill in the art upon review of this disclosure. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. While the present invention has been described in connection with a series of embodiments, these descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. It will be further understood that the invention is not necessarily limited to the discrete features or the order of the features described. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. 

1. An insert assembly for a weapon, the insert assembly comprising: a support plate that is received in a lower receiver of the weapon; a hollow protrusion rigidly attached to the support plate and extending upward relative to a top surface of the support plate; a piston inserted into the hollow protrusion, the piston sliding inside the hollow protrusion, the piston including a top surface to support a bolt of the weapon when the bolt slides over the top surface of the piston; and a spring inserted into the hollow protrusion between the piston and the top surface of the support plate, the spring exerting a force on the piston, thereby pushing the piston against the bolt.
 2. The insert assembly of claim 1, wherein the top surface of the piston is substantially parallel to the top surface of the support plate.
 3. The insert assembly of claim 1, wherein the hollow protrusion and the piston include aligning features to control the orientation of the piston with respect to the support plate.
 4. The insert assembly of claim 1, wherein the top surface of the piston includes a chamfer.
 5. The insert assembly of claim 4, wherein the chamfer locates a bolt keyway when the bolt moves reciprocally between two working positions during firing and reloading.
 6. The insert assembly of claim 1, wherein any of the support plate, the hollow protrusion, and the spring are made of stainless steel.
 7. The insert assembly of claim 1, wherein the hollow protrusion includes a positive stop feature to limit an upmost position of the piston.
 8. The insert assembly of claim 1, wherein the spring exerts a force of between about 5 lbs and about 15 lbs on the piston when the top surface of the piston is in an upmost position.
 9. The insert assembly of claim 1, wherein the spring exerts a force of about 10 lbs on the piston when the top surface of the piston is in an upmost position.
 10. The insert assembly of claim 1, wherein the piston extends out of the hollow protrusion about 0.5 inches when the top surface of the piston is in an upmost position.
 11. The insert assembly of claim 1, wherein the top surface of the piston conforms to a profile of the bolt.
 12. The insert assembly of claim 1, further comprising a second protrusion attached to the support plate and extending upward from the top surface of the support plate in the same direction as the hollow protrusion, the second protrusion including a second top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver.
 13. The insert assembly of claim 12, wherein friction maintains the insert assembly in position with respect to other components of the weapon.
 14. The insert assembly of claim 12, wherein the second top surface is formed from a compressible material.
 15. The insert assembly of claim 12, wherein the second top surface is formed from Santoprene™ TPV 111-35.
 16. The insert assembly of claim 12, wherein the second top surface extends upward from the second protrusion to engage the upper receiver of the weapon.
 17. The insert assembly of claim 12, wherein the second top surface compresses about 0.125 inches while engaging the upper receiver of the weapon.
 18. An insert assembly for a weapon, the insert assembly comprising: a support plate received in a lower receiver of the weapon; and a protrusion attached to the support plate and extending away from a top surface of the support plate, the protrusion including a top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver.
 19. The insert assembly of claim 18, wherein friction maintains the insert assembly in position with respect to other components of the weapon.
 20. An insert assembly for a weapon, the insert assembly comprising: a support plate that is received in a lower receiver of the weapon; a hollow protrusion rigidly attached to the support plate and upward relative to a top surface of the support plate; a piston inserted into the hollow protrusion, the piston sliding inside the hollow protrusion, the piston including a top surface to support a bolt of the weapon, the top surface of the piston including a chamfer to locate a bolt keyway when the bolt moves reciprocally between two working positions during firing and reloading; a spring inserted into the hollow protrusion between the piston and the top surface of the support plate, the spring exerting a predetermined force of between about 5 lbs and about 15 lbs on the piston, thereby pushing the piston against the bolt; and a second protrusion attached to the support plate, the second protrusion including a top surface that presses on an upper receiver of the weapon when the upper receiver is engaged with the lower receiver. 